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Birger Christensson asks:
>IS THERE ANYONE WHO BELIVES THAT FLOW CYTOMETRY IS A
>CLINICALLY USEFUL
>METHOD FOR THIS ANALYSIS IN ITP??
>ARE THERE ANY GOOD PROTOCOLS AVAILABLE AND IS THERE ANY
FOLLOW UP AS TO THE
>SENSITIVITY AND SPECIFICITY OF THIS OR OTHER THROMBOCYTE
TESTS IN ITP??
I am one who believes that flow cytometry is probably the best method to
measure platelet associated Ig (PAIg), and that this test, although far from
perfect, can be useful in evaluating patients with thrombocytopenia. The direct
assay for PAIg is easily performed, and I would be happy to share our
protocols. They have been published in the references listed below.
The "indirect" test, i.e. mixing patient plasma with normal platelets is not useful
in our hands. It has a very wide "normal range" as you have observed, and
seldom correlates with either the direct test or with disease. It may be useful in
the setting of "cross-matching" for platelet transfusion, but it is not very useful in
the diagnosis of ITP.
I strongly recommend that you combine the flow cytometric measurement of
PAIg with the measurement of "retcilated platelets" (platelets with increased
RNA as detected byThiazole Orange). Patients who have both elevated
reticulated platelets, and increased PAIg are very likely suffer from immune
thrombocytopenia, whereas an elevated PAIg alone may be seen in other
forms of thrombocytopenia.
Ault, K.A. 1988. Flow cytometric measurement of platelet associated
immunoglobulin. Path. and Immunopath. Res. 7:395-408.
Ault K. A., H. M. Rinder, J. Mitchell, M. B. Carmody, C. P. H. Vary, and R.S.
Hillman. 1992. The significance of platelets with increased nucleic acid content
(reticulated platelets): A measure of the rate of thrombopoiesis? Am. J. Clin.
Path. 98:637-646.
Rinder, H. M., U. J. Munz, K. A. Ault, J. L. Bonan, and B. R. Smith. 1993.
Reticulated platelets in the evaluation of thrombopoietic disorders. Arch.
Pathol. Lab. Med. 117:606-610.
Ault, K.A. and J. Mitchell. 1994. Analysis of Platelets by Flow Cytometry. In:
Methods in Cell Biology Volume 42, Flow Cytometry, Second Edition Part B. Z.
Darzynkiewicz, J.P. Robinson, and H.A. Crisman, Eds. Academic Press.
pp275-293.
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Kenneth A. Ault M.D.
Maine Medical Center Research Institute
125 John Roberts Road
South Portland ME 04106
Voice (207) 761-9090
Fax (207) 761-2130
E-Mail aultk.mmcri@office.mmc.org
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